Figure 1

(a) Spin state of the P donor electron in silicon is detected by monitoring the photocurrent. Electrons from the conduction band are trapped in the $D^{-}$ state only when they can form a singlet with the donor electron. The four eigenstates of the Si:P donor system are shown with large blue/dark gray arrows for the (spin 1/2) electron spin and smaller red arrows for the (spin 1/2) nuclear spin. The hyperfine interaction between the nucleus and electron lifts the degeneracy for the four transitions which can be driven using spin resonance. The nuclear spin state thus determines if resonance (and thus a change in the photocurrent) occurs at $f_1^e$ or $f_2^e$. Probing one of these transitions therefore allows the nuclear spin state to be determined. For the experiments reported here, $f_2^e=240$ GHz, $f_1^n=88.60$ MHz, and $f_2^n=201.24$ MHz. (b) An inversion-recovery experiment ($f_2^e$ - $\tau$ - $f_2^e$) is used to find the lifetime of the electron spin $T_1^e$ $=1.86\pm 0.02$ ms. The current change $\Delta I$ is the difference in the average current for the 200 $\mu$s before and after the final pulse.Reuse & Permissions

Figure 2

Pulse sequence for observing nuclear spin echoes. (a)–(d) Preparation of a polarized nuclear spin population is obtained by mapping the large electron spin polarization to the nuclear spins with a two-pulse sequence. (e) The nuclear spin echo is performed on the electron spin-down manifold. (f) Readout of the resulting nuclear spin population is achieved by selectively exciting the electron spins corresponding to nuclear spin down, and monitoring the current change through the sample after the excitation. (g) The change in current through the sample during an entire pulse sequence, with $\tau =0.5$ ms. (Light gray spins represent nominally unpopulated states.)Reuse & Permissions

Figure 3

Nuclear echoes. (a) The change in photocurrent following the readout pulse for an echo sequence with $\tau =1$ ms. A clear echo is seen when $\tau ={\tau }^{\prime }$. (b) The amplitude of the echo is plotted for a range of $\tau$. The data are fit with a simple exponentially decaying function, yielding a nuclear spin coherence time $T_2^n$ $=2.8\pm 0.4$ ms (red solid line). The data are fit nearly as well if $T_2^n$ is fixed to be 2$T_1^e$ (green dashed line). Note the logarithmic scale on the $x$ axis.Reuse & Permissions

Figure 4

Spin lifetime $T_1^e$ of phosphorus donor electrons measured with an inversion recovery sequence at a resonance frequency of 240 GHz with conventional pulsed electron spin resonance. The measurements are performed both in the dark (closed data points) and while shining light onto the sample (open data points).Reuse & Permissions